Local C–V mapping for ferroelectrics using scanning nonlinear dielectric microscopy

Yoshiomi Hiranaga,Takao Shimizu,Yasuo Cho,Takanori Mimura,Hiroshi Funakubo

doi:10.1063/5.0029630

Abstract

Detailed analysis of local polarization switching will promote the further development of a wide range of applications using ferroelectrics. Here, we propose a local C–V mapping technique using scanning nonlinear dielectric microscopy (SNDM) that enables visualization of dynamic ferroelectric switching behavior in real space. Using this method, C–V butterfly curves characteristic of ferroelectrics can be measured on a scanning probe microscopy platform with nanoscale resolution by virtue of the high capacitance-detection sensitivity of SNDM. This provides real-space mapping of the net switchable polarization, the switching voltage, and the local imprint with a short measurement time (e.g., 10 min or less for 256×256 pixels). Furthermore, the proposed method will be useful for study of the electric-field response of domain walls. In this paper, we present some examples of experiments with LiTaO3 single crystals and HfO2-based ferroelectric thin films and give an overview of what kind of evaluation is possible with the local C–V mapping technique.

Highlights

With the demand for innovative devices for the realization and development of the Internet-of-Things (IoT) society, ferroelectrics and piezoelectrics occupy an important position, having various applications such as non-volatile memories,[1,2] high-frequency filters,[3] sensors,[4] actuators,[5] and energy harvesters.[6]
We present some examples of experiments with LiTaO3 single crystals and HfO2-based ferroelectric thin films and give an overview of what kind of evaluation is possible with the local C–V mapping technique
We developed a local C–V mapping method for ferroelectrics based on scanning nonlinear dielectric microscopy (SNDM)

Summary

INTRODUCTION

With the demand for innovative devices for the realization and development of the Internet-of-Things (IoT) society, ferroelectrics and piezoelectrics occupy an important position, having various applications such as non-volatile memories,[1,2] high-frequency filters,[3] sensors,[4] actuators,[5] and energy harvesters.[6]. The SNDM-based local C–V mapping method proposed in this study can resolve all these problems This method uses a simple sinusoidal bias, as with G-VS, and allows the measurement of frequency dispersion. Since the response waveform is not affected by the frequency characteristics of the cantilever, once the electrical phase delay of the measurement system is calibrated, it is not necessary to recalibrate for each measurement In this way, the local C–V mapping proposed in this study has many advantages and can be a powerful tool in various applications. In local C–V mapping, a largeamplitude AC bias above the polarization-switching voltage is applied to the sample, and the response signal due to the capacitance deviation is acquired, including the higher-order harmonic components. It would be more precise to use the term “ΔC–V curve”; we choose to use the simpler term “C–V curve” in this paper. (As a further supplementary note, it is possible to determine the absolute capacitance by using another method named @C/@z-SNDM.[40,41] since the absolute capacitance is not necessary in the discussion of polarization switching, this is not discussed further here.)

Measurement samples

Depolarized LiTaO3 single crystal

Parameter mapping

CONCLUSION